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copenglglslshadertexture-mapping

GLSL Shader going black when I try to sample a texture

I render a triangle strip this way, and with basic bypass shaders all is working fine: EDIT: I added TextCoords and modified the shaders , I keep getting the same result, my 3d objects are going black!

UPDATED CODE:

// Dibuixem tots els prismes
    glBegin(GL_TRIANGLE_STRIP);
    for(i=0;i<num_elems;i++) {
        for(j=0;j<num_vertices;j++) {

            glNormal3fv((GLfloat *)(a+j*2));
            glTexCoord2f(0.0f, 0.0f); 
            glVertex3fv((GLfloat *)(a+j*2+1));
            glTexCoord2f(1.0f, 0.0f); 
            glNormal3fv((GLfloat *)(b+j*2));
            glTexCoord2f(1.0f, 1.0f); 
            glVertex3fv((GLfloat *)(b+j*2+1));
        }

        glNormal3fv((GLfloat *)(a));
        glTexCoord2f(0.0f, 1.0f);
        glVertex3fv((GLfloat *)(a+1));
        glNormal3fv((GLfloat *)(b));
        glTexCoord2f(0.0f, 0.0f); 
        glVertex3fv((GLfloat *)(b+1));
        a+=face_size;
        b+=face_size;
    }
    glEnd();

And I am trying to attach a texture to my shaders, but I can't figure out how to pass the texture.

I create and add the texture to my program this way. Texture data is verified array with format unsigned char data[imageSize];:

   GLuint textureID;
   glGenTextures(1, &textureID);
   glBindTexture(GL_TEXTURE_2D, textureID);
   glActiveTexture(GL_TEXTURE0); // Texture unit 0
   glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
   glTexImage2D(GL_TEXTURE_2D, 0,GL_BGR, width, height, 0, GL_BGR, GL_UNSIGNED_BYTE, data);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
   GLuint VertexShaderID = glCreateShader(GL_VERTEX_SHADER);

This is what I read in another posts with the same issue and I added to my code after compiling my shaders and generating my program without errors. Tutorials tend to dismiss this information (how you say to your shader the name and location of your binded texture).

GLuint t1Location = glGetUniformLocation(programID, "tex1");
glUniform1i(t1Location, 0);

And my shaders UPDATED CODE:

#define GLSL(version, shader) "#version " #version "\n" #shader
const char* vert = GLSL
(
    110,

    varying vec4 position;
    varying vec3 normal;
    varying out vec4 texCoord;
    varying vec2 coord;
    void main()
    {
        position    = gl_ModelViewMatrix * gl_Vertex;
        normal      = normalize( gl_NormalMatrix * gl_Normal.xyz );
        gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
        coord       = vec2(gl_MultiTexCoord0);
    } 
);


    


const char* frag  = GLSL
(
    110,
        
    uniform sampler2D tex1;
    varying vec4 position;
    varying vec3 normal;
    varying vec2 coord;
    
    void main()
    {
         gl_FragColor = texture2D(tex1, coord);
    } 
);

EDIT2:

I am setting up gl this way:(maybe something is conflicting with my texture shader, but I don't think so!

 /* set up depth-buffering */
   glEnable(GL_DEPTH_TEST);

   glEnable(GL_POLYGON_SMOOTH);
   glHint(GL_POLYGON_SMOOTH_HINT, GL_FASTEST);

   /* set up lights */
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();

   glPolygonMode(GL_FRONT_AND_BACK,GL_FILL);
   glShadeModel(GL_SMOOTH);

   GLfloat lightpos[]   = { 3.0, 0.0, 1.0, 0.0 };
   GLfloat lightcolor[] = { 0.5, 0.5, 0.5, 1.0 };
   GLfloat ambcolor[]   = { 0.5, 0.5, 0.5, 1.0 };

   glLightModelfv(GL_LIGHT_MODEL_AMBIENT,ambcolor);

   glEnable(GL_LIGHTING);
   glColorMaterial(GL_FRONT_AND_BACK,GL_AMBIENT_AND_DIFFUSE);

   glEnable  (GL_COLOR_MATERIAL);
   glLightfv (GL_LIGHT0,GL_POSITION,lightpos);
   glLightfv (GL_LIGHT0,GL_AMBIENT,ambcolor);
   glLightfv (GL_LIGHT0,GL_DIFFUSE,lightcolor);
   glLightfv (GL_LIGHT0,GL_SPECULAR,lightcolor);
   glLightf  (GL_LIGHT0,GL_CONSTANT_ATTENUATION,0.2);
   glLightf  (GL_LIGHT0,GL_LINEAR_ATTENUATION,0.0);
   glLightf  (GL_LIGHT0,GL_QUADRATIC_ATTENUATION,1.0);
   glEnable  (GL_LIGHT0);
   glEnable(GL_TEXTURE_2D);

Replacing gl_FragColor by a flat color is working fine. I know maybe is related to coord parameter but I am trying all the stuff I found and nothing is working for me.

Solution

  • The internal texture format GL_BGR is not valid. GL_BGR is a valid for the format of the source texture, but the internal representation has to be GL_RGB.
    See glTexImage2D.

    Adapt your code like this:

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_BGR, GL_UNSIGNED_BYTE, data);

    See the Khronos reference page GLAPI/glTexImage2D which says:

    To define texture images, call glTexImage2D. The arguments describe the parameters of the texture image, such as height, width, width of the border, level-of-detail number (see glTexParameter), and number of color components provided. The last three arguments describe how the image is represented in memory.

    format​ determines the composition of each element in data​. It can assume one of these symbolic values:

    GL_BGR: Each element is an RGB triple. The GL converts it to floating point and assembles it into an RGBA element by attaching 1 for alpha. Each component is clamped to the range [0,1].